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Search Results: 1 - 10 of 879 matches for " Shohei Miyazaki "
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Quantitative Assessment of the Effect of Nitric Oxide Synthase Inhibition on Tumor Vascular Activity Using Dynamic Contrast-Enhanced Computed Tomography  [PDF]
Kenya Murase, Yoshinori Kusakabe, Shohei Miyazaki
Open Journal of Medical Imaging (OJMI) , 2016, DOI: 10.4236/ojmi.2016.62005
Abstract: Purpose: The purpose of this study was to develop a method to quantitatively assess the effect of nitric oxide synthase (NOS) inhibition on tumor vascular activity using dynamic contrast-enhanced computed tomography (DCE-CT) and to investigate its usefulness using animal experiments. Mate-rials and Methods: The DCE-CT studies were performed in anesthetized Fisher rats bearing tumors using a 4-row multi-slice CT. The scanning started 4 s before a bolus injection of iodinated contrast agent (CA) (150 mgI/kg) from the tail vein using an automatic injector and lasted 60 s at 1-s in-tervals. The contrast enhancement (CE) images were generated by subtracting the CT images before and after the administration of CA. First, the DCE-CT studies were performed before and 15, 30, and 45 min after administration of N-nitro-L-arginine (L-NNA) (1, 3, and 10 mg/kg) or vehicle, and the relative CE values were calculated by normalizing the CE image at each time point by that obtained from the first DCE-CT study. Second, we investigated the case when L-arginine (L-ARG) (200 mg/kg) and L-NNA (1, 3, and 10 mg/kg) were administered after the first and second DCE-CT studies, respectively. Third, we investigated the case when L-NNA (1, 3, and 10 mg/kg) and L-ARG (200 mg/kg) were administered after the first and second DCE-CT studies, respectively. Finally, we investigated the case when L-NNA (1, 3, and 10 mg/kg) and L-ARG (200 mg/kg) were administered simultaneously after the first DCE-CT study. Results: The relative CE value significantly decreased after L-NNA administration in a dose-dependent manner (p-values = 0.0074 and <0.0001 for 0 vs. 3 mg/kg and 0 vs. 10 mg/kg, respectively, at 15 min, 0.0003 and <0.0001 for 0 vs. 3 mg/kg and 0 vs. 10 mg/kg, respectively, at 30 min, and 0.0367 and 0.0004 for 0 vs. 3 mg/kg and 0 vs. 10 mg/kg, respectively, at 45 min). When L-ARG was administered prior to the administration of 1 mg/kg L-NNA, the relative CE value at 45 min was significantly higher than that at 15 min. When L-ARG was administered after L-NNA administration, there was no significant difference between the relative CE values at 15 min and 45 min. These results suggest that when using L-NNA in combination with L-ARG, their effect on tumor vascular activity differs depending on the order of their administration. When L-NNA and L-ARG were administered simultaneously, there was a tendency for the relative CE value to be higher than that when only L-NNA was administered, at all injected doses of L-NNA. Conclusion: Our method using DCE-CT is useful for monitoring the effect
Quantitative Assessment of Protective Effects of Antioxidant Agents against Drug-Induced Nephrotoxicity Using Dynamic Contrast-Enhanced Computed Tomography  [PDF]
Kenya Murase, Akihiro Kitamura, Atsushi Tachibana, Yoshinori Kusakabe, Risa Matsuura, Shohei Miyazaki
Open Journal of Medical Imaging (OJMI) , 2016, DOI: 10.4236/ojmi.2016.63006
Abstract: Purpose: The purpose of this study was to develop a method for quantifying the extent of renal dysfunction due to drug-induced nephrotoxicity using dynamic contrast-enhanced computed tomography (DCE-CT) and to investigate the protective effects of various antioxidant agents against cis-dichlorodiammineplatinum (cisplatin)-induced nephrotoxicity in rats using this method. Materials and Methods: The DCE-CT studies were performed in 8-week-old male Sprague-Dawley rats. The CT scanning started 4 s before a bolus intravenous injection of iodinated contrast agent (CA) (150 mgI/kg) from the tail vein using an automatic injector and lasted 90 s at 1-s intervals. The contrast clearance per unit renal volume (K1) was estimated from the DCE-CT data using the Patlak model. The renal volume (V) was calculated by manually delineating the kidney on the CT image. The contrast clearance of the entire kid-ney (K) was obtained by . First, to investigate the effect of CA itself, the DCE-CT studies were performed without injecting cisplatin 2, 4, and 7 days after the first DCE-CT study on day 0. Second, to investigate the effect of injected dose of cisplatin, the DCE-CT study was performed after the intraperitoneal (i.p.) injection of cisplatin (1.8 mg/kg) and was repeated every other day for one week. Finally, to investigate the protective effects of antioxidant agents [L-arginine (300 mg/kg), N-acetylcysteine (500 or 1000 mg/kg), methimazole (40 mg/kg), captopril (60 mg/kg), and taurine (750 mg/kg)], the DCE-CT studies were performed on days 0, 2, 4, and 7 after the i.p. injection of cisplatin (3.6 mg/kg). For comparison, the DCE-CT data were also acquired without injecting the antioxidant agents (CDDP group). Results: When cisplatin was not injected, there were no significant changes in the K value as compared to that on day 0 within the studied period. The K valuesignificantly (p < 0.05) decreased with increasing dose of cisplatin. Although some differences were observed in the extent of change in the K value normalized by that on day 0, depending on the antioxidant agents and their injected dose and schedule, the normalized K values on day 7 in the groups injected with the antioxidant agents were significantly higher than those in the CDDP group, suggesting that the antioxidant agents studied here had protective effects against cisplatin-induced nephrotoxicity in varying degrees. Conclusion: Our method appears useful for quantitatively evaluating the protective effects of antioxidant agents against cisplatin-induced nephrotoxicity and for investigating the optimal
Dust Resulting from Tire Wear and the Risk of Health Hazards  [PDF]
Masakazu Yamashita, Shohei Yamanaka
Journal of Environmental Protection (JEP) , 2013, DOI: 10.4236/jep.2013.46059
Abstract:

The present study examined the effects of air pollutants on people’s health, focusing on dust produced from automobile tires while cars drive on roads. The annual volume of dust resulting from tire wear, calculated based on the number of automobiles registered in Japan, was 1747245.4 m3. To put it simply, this translates to approximately 1.4 times the volume of the Tokyo Dome, a famous Japanese baseball stadium. Particulate substances are categorized into three groups depending on their size, and dust resulting from tire wear is classified into the coarse particle mode along with mold spores, pollen, and dust produced from brake pads. This study examined whether or not tire dust causes health damage similarly to pollen, a particulate substance in the same group. There were 38/cm2 dust particles resulting from tire wear on a busy road in Osaka Prefecture, and this number was larger than that of cedar pollen/cm2 (35), a cause of hay fever, identified in Hokkaido. The results suggest that tire dust may also adversely affect the health of people if any of its constituents has a toxicity or causes allergies.

The Effects of Trait Rumination and Reflection on Mental Health among Japanese University Athletes  [PDF]
Shohei Yamakoshi, Hironobu Tsuchiya
Psychology (PSYCH) , 2016, DOI: 10.4236/psych.2016.74054
Abstract:

The purpose of this study was to use structural equation modeling to examine the effects of trait rumination and reflection on stress response and subjective well-being among Japanese university athletes. One hundred and eighty-two Japanese university athletes (114 males, 68 females, mean age = 20.15 years) participated. Trait rumination was positively associated with stress response and negatively associated with subjective well-being. On the other hand, trait reflection showed a negative association with stress response and a positive association with subjective well-being. In order to develop effective interventions for athletes high in rumination and/or low in reflection, future research should examine the mechanism that explains the different effects of rumination and reflection on athlete mental health.

A Comment on Reis  [PDF]
Kenji Miyazaki
Theoretical Economics Letters (TEL) , 2011, DOI: 10.4236/tel.2011.13019
Abstract: This note gives a counterexample on Reis [1]. Using a certain family of utility functions, this note not only gives a sharper representation than that of Reis but also demonstrates that interest rate inelastic money demand does not lead to superneutrality. This implies that superneutrality does not exist when uncerinty is introduced.
Incentives in Public and Privatized Firms under Incomplete Contracting Situations  [PDF]
Takeshi Miyazaki
Theoretical Economics Letters (TEL) , 2012, DOI: 10.4236/tel.2012.23059
Abstract: It is argued that incentives for employees in the public service agencies will necessarily be weak because of the multiple dimensions of products, multiple principals, incomplete contract, and socializing. Some empirical studies refer to incomplete contracting situations as part of the cause of the diminishing of the public sector. This work investigates the effects of privatization and ownership shares on incentive schemes for employees who work for public or privatized firms under incomplete contracting situations. Two main results are obtained. First, the incentive intensity of public firms decreases as the government has more ownership shares, and the social benefit declines. Second, privatized firms offer their employees higher-powered incentive contracts than do public firms.
A Computational Model Associating Learning Process, Word Attributes, and Age of Acquisition
Shohei Hidaka
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0076242
Abstract: We propose a new model-based approach linking word learning to the age of acquisition (AoA) of words; a new computational tool for understanding the relationships among word learning processes, psychological attributes, and word AoAs as measures of vocabulary growth. The computational model developed describes the distinct statistical relationships between three theoretical factors underpinning word learning and AoA distributions. Simply put, this model formulates how different learning processes, characterized by change in learning rate over time and/or by the number of exposures required to acquire a word, likely result in different AoA distributions depending on word type. We tested the model in three respects. The first analysis showed that the proposed model accounts for empirical AoA distributions better than a standard alternative. The second analysis demonstrated that the estimated learning parameters well predicted the psychological attributes, such as frequency and imageability, of words. The third analysis illustrated that the developmental trend predicted by our estimated learning parameters was consistent with relevant findings in the developmental literature on word learning in children. We further discuss the theoretical implications of our model-based approach.
Experimental Prospects for B -> X(s/d)gamma and B -> X(s)l+l-
Shohei Nishida
Physics , 2011,
Abstract: In this report, experimental prospects for the inclusive analysis of the radiative B decays and electroweak penguin decays at the super B factories are presented.
Matrix product is many-sorted algebra
Shohei Izawa
Mathematics , 2013,
Abstract: It is known that a category of many-sorted algebras on pure sets of similarity type is "concretely equivalent" to a category of single-sorted algebras. In this paper, we characterize a single-sorted variety that corresponds to a many-sorted variety. Such variety is also characterized by the condition that is decomposable with respect to matrix product.
Recursive Markov Process
Shohei Hidaka
Mathematics , 2015,
Abstract: A Markov process, which is constructed recursively, arises in stochastic games with Markov strategies. In this study, we defined a special class of random processes called the recursive Markov process, which has infinitely many states but can be expressed in a closed form. We derive the characteristic equation which the marginal stationary distribution of an arbitrary recursive Markov process needs to satisfy.
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